All aspects of manufacturing are striving to reduce the time between concept and finished product. Conventional methods of manufacture includes the steps of design, clay models, making of a prototype mold, followed by a short run of manufactured articles, and finally the production of a stainless steel mold, casting or stamping for production utilized to produce a large number of finished products.
Traditionally, in the manufacture of automotive parts, a prototype mold or stamping is made of a zinc-based alloy, such as zinc-based alloy KIRKSITE. Generally these molds or stampings yield about one thousand to six thousand parts before the mold or stamping loses its efficacy. After several thousand parts are either molded or stamped on such a prototype molding or stamping, the last parts being manufactured are no longer within specifications. Consequently, as the tolerances are no longer being met, the prototype mold becomes useless, as repairing the casting or mold is not feasible. The forming edges usually become dull with use. Generally, these prototype molds are not recyclable, rendering the entire used mold useless. After the prototype mold or stamping has been used up, at a cost of from about $500 to about $20,000, a production molding or stamping from steel would be made.
The production molds or stampings have a much greater cost, from about $2,000 to $500,000, depending on the size of the part being manufactured, the number of cavities in the mold, along with other considerations. These production molds can take weeks or months to make. This litany of steps has made the lead time between design and production last up to two years or more.
In the automotive industry, it is desirable to shorten the lead time. One way to do this is to shorten the time that is required to make the molds or stampings, or, to eliminate one of the steps altogether. The automotive companies want to reduce the time between design and production to less than ninety days. By using new technology, they have eliminated certain steps including the clay model making step with CAD-CAM computer systems in communication with CNC grinders, which cut out the moldings or stampings.
The next logical step for shortening the lead time between design and production would be to prolong the usefulness of the prototype mold beyond the initial parts that it is capable of making. As most car parts require runs of up to 200,000 parts, new materials are needed for the molds or stamps in order to add durability. The necessary properties for such a new material would include a high compressive and tensile strengths, as well as other durability properties. In addition, the new material must be pourable, castable and machinable. Previous attempts to make such a new material have yielded Zn--Cu--Al alloys which exhibit Birnell hardnesses of about 50-75, while production steel molds and stampings exhibit hardnesses beyond the Birnell scale (generally less than 150), with their actual hardness values extend into the "B" scale (generally more than 150 on the Birnell hardness scale).
Therefore, it would be a real advantage to provide a new material which would exhibit these properties, while still being pourable, castable, and machinable, as well as castings made therefrom.